Several methods for attaching a cushion material which is made of a foamed body forming a body portion of a car seat and a skin material attached on its surface have been known and publicly used. Specifically as a method of attaching a skin material to a cushion material with a concave surface, a back surface of the skin was bonded over a surface of the cushion material or an integral molding method of injecting urethane into a cushion material molding die after setting a skin material have often been used. However, in either method, their own production systems for carrying out such methods are required and it is difficult to install such systems in a continuous assembly line, thereby increasing the cost for transferring and manipulating materials. Also, such a method in the art is a mass production system and it is thus required to maintain its operation rate. However it is difficult to control a volume corresponding to a variation of the production rate. Thus, such a production method results in low productivity and causes a rise in cost.
It is intended to use a planar fastening material in order to facilitate attaching a skin material to a cushion material to eliminate the above problems. The planar fastening material is so called a planar fastener and has innumerable hooked or ring-shaped small protrusions imbedded on a knitted or textile base sheet. The hooked or ring-shaped small protrusions fasten and mechanically attach to a back side of the skin material. However, in this mechanical attachment of the skin by the planar fastening material, unexpected troubles are found in practice.
Explaining the troubles with reference to FIG. 4, when a person gets off a seat 15, a tensile force as indicated by an arrow F1 acts on a skin 16. Since the skin 16 is attached on the planar fastening material 17 by the mechanical tensile force, the skin is instantaneously separated from the planar fastening material, when a component F2 of the tensile force F1 exceeds the mechanical attachment force. However, if the force F1 is reduced by movement of the person, then the skin is immediately fastened to the planar fastening material to revert to its initial state again. Such a repetition of separating and fastening produces noise or vibration, and users may have distrust of the quality of the seat and they may also feel displeasure and wariness. Also, they may mistake the noise for static electricity.